Johnny Manziel Clubbin' with Future & Drinking Champagne

Johnny Manziel put his NFL comeback on hold Thursday night to party in Miami with rap superstar Future ... and it appears he's drinkin' again too.

Manziel and Future turned all the way up at STORY nightclub -- where the ex-NFL quarterback got onstage and hung with Future's entourage.

As for the boozing, earlier in the night Manziel Snapchatted a clip of someone pouring him a glass of champagne. It appears he drank it ... despite his vow to go sober while he trains to get back in the NFL.

Manziel has been in Miami for a couple of days ... on Wednesday, he went to see Drake and Future in concert.

He was rockin' OVO gear, an OVO chain and had a VIP pass hanging around his neck -- so, we're guessing he's still on good terms with his old pal Drake.